Many different types of arrows and arrow shafts are known for use in hunting and sport archery. Two arrow types of relatively recent design are the fiber reinforced polymer (FRP) arrows and the aluminum arrows wrapped with fiber reinforced polymer. FRP is a generic term including, but not limited to, fiberglass composites and carbon fiber composites. Aluminum arrow shafts covered with fiber reinforced polymer are usually made of an aluminum core covered with carbon fiber and are often referred to as aluminum carbon composite (ACC) arrows, although any fiber reinforced polymer may be used as the covering. Traditional FRP and ACC shafts have been produced by a number of different manufacturing processes. The first FRP arrow shafts were constructed with unidirectional reinforcing fibers aligned parallel to the axis of the shaft.
Prior designs and processes for constructing FRP shafts resulted in a low circumferential or hoop strength. The hoop strength of these arrow shafts was so low that the arrows could not withstand even small internal loads applied in a direction radially outwardly from the center of the shaft. For example, internal loads generated from inserting standard components into the inside of these types of shafts would have resulted in failure of the arrow shaft. Standard arrow components, such as those shown in FIG. 1, include inserts 100, points 116 (“point” as used herein means any structure formed at or secured to the forward or distal end of the arrow, including without limitation field points, broadheads, etc.), and nocks 102, all of which are mounted to an arrow shaft 104. It should be noted that fletching, required for proper arrow flight, is not shown in the drawings, but is well understood by those skilled in the art.
Because insert components have not been practical for use with the relatively small diameter FRP prior art shafts of types discussed above, externally attached components have been developed and used. FIG. 2 illustrates two such external components, known as “outserts” in the industry. The term “outsert,” as it suggests, refers to an arrow component that is inserted or installed over the outside diameter of the arrow. The two outserts shown in FIG. 2 include an outsert receptacle 200 to receive a point 116 and an outsert nock 202. Outserts were, at the time, the only viable way to attach the various other arrow components to these prior FRP shafts because of their low hoop stress. Arrow shaft outserts have, however, at least three key disadvantages. First, outsert nocks 202 have a feel that is objectionable to most archers. Generally, archers prefer a smooth outer surface of the shaft without any projections (other than the fletching). This smooth outside diameter preference correlates with the general understanding that an arrow will have better aerodynamic efficiency with fewer structural projections outside of the arrow shaft.
Second, outsert nocks 202 frequently result in mechanical interference with many types of arrow rests when launching the arrow. Most arrow rests hold the arrow in a particular position when the archery bow is drawn and the arrow is released. With many arrow rests, the arrow continues to contact the arrow rest as the arrow passes the location of the arrow rest. Contact between the nock outsert and the arrow rest can result in unpredictable disturbances during launch of the arrow, and therefore will affect the accuracy of the shot.
Third, the point outsert 200 has a larger diameter relative to the diameter of the shaft, which makes the arrows containing the point outsert 200 more difficult to extract from various targets as compared to arrows with insert components only. Use of the point outsert 200 often results in damaged points and outserts 200, and further causes points and outserts 200 to detach from the arrow shaft and remain inside the target after the arrow is pulled from the target. Points and/or outserts 200 lost inside a target may cause damage to subsequent arrows that happen to impact the target at the same location as the lost points or outserts. As a result, some commercial archery ranges have banned outsert-equipped arrow shafts.
In an apparent attempt to address the limitations described above, modern FRP arrows with new types of construction have been developed. The typical modern FRP arrows include glass and/or carbon fibers arranged in multiple directions, as opposed to the unidirectional fiber arrangement of the earlier FRP arrows. The multi-directional fiber arrangement (e.g., fibers that run perpendicularly or at an angle relative to each other) increases the hoop strength of the shafts, which allows the shafts to support greater internal loads, including internal loads generated by insert components. Such modern FRP arrows have, however, been traditionally made having an outside diameter and wall thickness of a size sufficient to accommodate standard-sized inserts. These carbon-composite arrows were generally lighter than aluminum shafts, but were generally of the same spine. “Spine” is an industry-standard measurement of arrow shaft stiffness. Spine is measured according the parameters shown in FIG. 3. As shown, a shaft 304 is supported at two points 306 and 308, which are separated by a distance of 28 inches. A 1.94-pound weight is applied at a mid point 310 of the shaft 304. The deflection 312 of the shaft 304 relative to the horizontal is defined as the “spine.” An arrow must have certain spine characteristics, depending on its length and the draw weight of the archery bow, to achieve proper flight. Generally, the heavier the draw weight, the stiffer the spine (i.e., less deflection) must be. ACC shafts are also generally lighter than standard aluminum arrows of the same spine because they comprise a thin, light core wound with carbon composites.
As a major portion of the archery market has moved toward lighter weight shafts, the modern FRP and ACC arrow have gained widespread acceptance. Lighter arrow shafts have the principal advantage of higher velocities when launched from the same bow. Such higher velocities result in a flatter arrow trajectory. The practical advantage of flatter trajectory is that a misjudgment by an archer of the range to a target has less effect on the point of impact.
Due to material and structural considerations, however, in designing internal-component FRP and ACC arrow shafts for reduced weight, it became necessary to both increase shaft outside diameter and reduce wall thickness relative to the prior art FRP and ACC outsert shafts in order to provide desirable spine/weight combinations. For aluminum arrow shafts, for example, to provide lighter weight arrows, the wall thickness must be reduced and the diameter of the arrow, both the inside diameter and the outside diameter, must be increased to maintain adequate spine. This process of thinning the wall and increasing shaft diameter has, however, practical limitations. At some point, if taken to an illogical extreme, the arrow would have mechanical properties similar to an aluminum beverage can with no practical resistance to side loads or crushing.
With some arrows, inserts, such as “half-out” inserts, were introduced to the market some time ago. A typical half-out insert assembly is shown in FIG. 4A. A half-out insert 400 includes a first insert portion 412 with a diameter smaller than the standard insert 100 shown in FIG. 1 such that the first insert portion 412 may be inserted into a reduced diameter shaft 404. A second portion 414 of the half-out insert 400 has a larger outside diameter that is receptive of a standard point 416, yet its outside diameter corresponds to the outside diameter of shaft 404. Therefore, half-out inserts facilitate use of standard field points with arrow shafts having inside diameters smaller than standard  arrow shafts.
Half-out assemblies have, however, several disadvantages and have not been well accepted. Half-out assemblies are cantilevered at the front of the arrow shaft 404. The cantilever results in a system that tends to deform more readily on impact as compared to other arrow assemblies. The half-out assemblies also make it more difficult to precisely align points 416 with the shaft 404, as will be discussed below in greater detail.